Antenna system



APatented Oct. 17, 1944 UNITED STATES PATENT OFFICE 2,360,726 i f vANTENNA SYSTEM Barton T. Setchell, St. Paul, Minn.

Application June 25, 1942, Serial No. 448,347

(Cl. 25m-x20) 3 Claims.

My invention relates to an improvement in antenna systems, wherein it isdesired to employ the ear-phones or speaker unit of a radio receivingset as the antenna for .the set.

In the use of portable receiving sets, difficulty has been experiencedin providing an antennaV and yet which will not interfere with thesimple portability of the set. For example when radio receiving sets arecarried continuously it has been common practice to either carry anupwardly projecting metal rod or buggy-whip type antenna, or to carryloops, coils, or lengths of antenna wire to be attached in any desiredposition on the carriers person.

v It is the object of the present invention to provide a radio receivingset which requires no antenna other than the ear phones or speaker unitused in conjunction with the set. As a result no extra antenna wire isrequired and the problem of attaching a suitable antenna to the carrieris obviated.

I have found that if the ear-phones or speaker unit are separatedfromthe output plate terminal by a suitableinductance capable ofallowing audio frequencies to pass through and capable of stopping orchoking radio frequencies, the earphones or speaker unit may be used asthe radio aerial. As a result no extra antenna is required.

A feature of the present invention lies in the provision of an antennacoil which is designed for best reception after the type of phones orspeaker and the length of phone cord used has been selected. Thisantenna coil is connected to the phones or speaker which in turn areconnected in any suitable manner with the output from the last tube ofthe radio receiver through the radio frequency choke coil. The B-batteryconnection to the plate of the output tube is so arranged that thisbattery will not short circuit through the phones. This result may beattained either by connecting the positive Bfbattery terminal to theplate through the primary of an output transformer, or by placing acondenser in the circuit between the positive B-battery terminal and theground.

A further feature of the present invention lies in the provision of acapacitor between the output plate and the radio frequency choke whichwill permit the by-passing of radio frequencies without substantiallyalecting audio frequencies.

Theseand other objects and novel features of my invention will be moreclearly and fully set forth in the followingspecication and claims.

In the drawing forming a part of my specification: y

v Figure 1 illustrates diagrammatically a receiving setcircuit embodyingthe use of ear-phones or a speaker unit as the aerial.

Figure 2 isa diagrammatic view showing a slightly different outputcircuit from that illustrated in Figure 1.

Figure 3 is a diagrammatic View showing another modied form ofconstruction showing the use of a resistor in the output circuit inplace of an output coil.

Figure 4 is a diagrammatic View showing a modied form of input circuit.

Figure 5 is a view similar to the remaining ligure, showing anothermodied form of input and output circuit.

Figure 6 is a diagrammatic view showing still another arrangement ofinputk circuit.

The circuit illustrated in Figure -1 of the drawing comprises a radioreceiving set which is outlined in general by a broken line andindicated by the letter A. This radio receiving set is illustrated onlyto show one type of circuit which may be used to embody the principlesof the present invention and it should be understood that any other typeof receiving set could be substituted for that illustrated.

The radio receiving set A is illustrated as comprising an input tube Illwhich may be of the 1T4 type, and the input terminal II is connected tothe grid I2 of the tube I0 by a suitable conductor. The plate I3 of thetube I0 is connected by conductor I4 to one coil of the radio frequencytransformer I5, the other terminal of which coil is connected byconductor I6 through the resistor II to the positive terminal I9 of theB-battery supply. The'grid 20 of the tube Ill is connected by conductor2| to the B-battery positive terminal I9 through the conductor I6 andresistor II. The tube filament is connected to a -suitable source ofcurrent supply.

`|I'he othercoil of the radio frequency transformer I5 is connected byconductor 22 tothe grid 23 of the mixer tube 24 which may be of the 1R5type. A conductor 25 connected to the conductor 22 passes through avariable condenser 26 tothe ground. The plate 2'I of the tube 2l'isconnected by conductorv 29 to one terminal of one 30. A Yconductor 3Iincludnga variable condenser 32 extends betweenthe ends of this coil ofthe transformer A3|). is connected by conductor 33 through the in- Vductance coil 34 and conductor 35 to ther con-Y coil of the intermediatefrequency transformer The other coil terminalY ductor I6 leading throughthe resistor I1 of the positive terminal of the B-battery. The conductorI6 is connected to the ground through a condenser 36.

'Ihe grid 31 of the tube 24 is connected b-y conductor 39 to theconductor 33. The grid 40 is connected by conductor 4| through theresistorA 42 to the ground. A detector crystal 43 is connected betweenthe conductor 33 and the conductor 40.

The other coil of the transformer 3U is connected by conductor 44 to thegrid 45 of the intermediate frequency tube 46 which may be of the 1T4type. The other terminal of this coil is connected by conductor 41through a resistor 49 to the ground. A variable condenser 50 isconnected between the conductors 44 and 41. The conductor 41 isconnected to the ground through a condenser The plate 52 of the tube 46is connected by conductor 53 to one terminal of one intermediatefrequency coil of the intermediate frequency transformer 54. The otherterminal of this coil is connected by conductor 55 to the positive B-battery terminal I9. A variable condenser 56 is connected between theends of this intermediate frequency coil and the conductor 55 isconnected by a conductor 51 to the grid 59 of the tube 46.

The other coil of the transformer 54 is connected by conductor 6I) tothe diode 6| of the tube 62 which may be of the 1S5 type. A variablecondenser 63 is connected between the terminals of this coil. The othercoil terminal is connected by a conductor 64 through the variableresistor 65 to the ground. The conductor 64 is also connected byconductor 66 through the resistor 61 to the automatic volume controlterminal 69. The conductors 64 and 66 are separated from the ground bythe condenser 10.

The variable arm 1| of the variable resistor 65 is connected through thecondenser 12 and the conductor 13 to the grid 14 of the tube 62. Theconductor 13 is connected through the resistor 15 to the ground. Theplate 16 is connected by conductor 11 through the resistor |9 to thepositive B-battery terminal I9. The grid 96 of the tube 62 is connectedby conductor 8| through the resistor 82 to the positive B-batteryterminal I9. The conductor 8| is separated from the ground by acondenser 83.

The conductor 11 is connected through the condenser 85 to the grid 86 ofthe output tube 81 which may be of the 154 type. The grid 86 isconnected through the resistor 89 to the negative terminal of theC-battery supply. The plate 9i) of the tube 81 is connected by theconductor 9| to the output terminal 92. The grid 93 is connected by theconductor 94 to the positive B-battery terminal I9. The filaments of allof the various tubes are connected to a suitable current supply.

As was previously pointed out the radio receiving unit outlined by thebroken line in Figure l of the drawing is merely illustrative of oneform of receiver which may be used, and any suitable receiver may besubstituted therefor, as will be clearly understood. The input terminalto the grid of the input tube, the output terminal 92 connected to theplate of the output tube 91, and the positive B-battery terminal I9 arethe only essential connections to the various input and output circuitswhich will be later described. The automatic volume control terminal 69is ordinarily desirable, but may in some instances not be required. l

'Ihe ear-phones 95 are connected by conductor 96 through the antennacoil 91 to the conductor 99 leading to the ground connection |90 to thecoil IUI of the input transformer, which is connected by conductor |62to the input terminal and is connected by conductor |03 to the A. V. C.terminal 69. The conductor |93 is connected through the condenser |94 tothe ground. rIhe conductor |92 isA connected through the: variablecondenser |05 to the ground.

The other phone cord or conductor |96 is connected to the radiofrequency choke |91, the other terminal of which is connected to thecoil |99 of the output transformer, and the other terminal of which isconnected by conductor ||9 to the ground. The conductor between thechoke coil |91 and the transformer coil `|69 is connected through theconductor I I2 to the ground.

The other coil I|3 of the output transformer has one terminal thereofconnected by conductor ||4 tothe output terminal 92 and has its otherterminal connected by conductor I |5 to the positive B-battery terminalI9.

It will be noticed that one terminal of the phones passes through theantenna coil 91 to the ground, while the other terminal thereof isconnectedthrough the radio frequency choke |91 to the secondary of theoutput transformer, the opposite terminal of which is grounded.-y Theantenna coil 91 is designed for best reception after the length of thephone cords and the type of phones to be used has been selected. Theradio frequency choke is any type of inductance coil of such inductanceas to allow audio frequencies to pass through and to choke or stop radiofrequency passage, The radio frequencies are bypassed to ground throughthe capacitor I I2 which will not substantially affect audiofrequencies.

I have found that with this arrangement the head phones 95 may beeffectively used as an aerial and that no other antenna is required.Thus the necessity for a separate aerial is entirely obviated.

In Figure 2 of the drawing I show a slightly different form of outputcircuit from that above described. In this form of construction the headphones H6 are provided with one cord or conductor |I1 leading throughthe antenna coil ||9 to the ground. The other coil |26 of the antennatransformer has one terminal connected by conductor |2| to the inputterminal leading to the grid of the input tube. A variable condenser |22is connected between the conductor |2| and the ground. The otherterminal of the coil |26 is connected by conductor |23 to the A. V. C.terminal 69. This conductor |23 is connected through the condenser |24to the ground. Thus the input circuit is similar to that shown in Figurel.

The other phone cord |25 is connected through the radio frequency chokecoil |26 which is isolated by the condenser |21 from the conductor |29leading through the inductance coil |30 to the positive B-batteryterminal I9. The conductor |3| between the choke coil |26 and thecondenser |21 is connected to ground through the condenser |32.

In this construction it will be noted that one phone cord extendsthrough the antenna coil which is vproperly designed for the particularhead phones and length of phone cord used. The other phone cord |25 isconnected through the choke coil |26 to the output terminal of thereceiving set passing through the condenser |21. The condenser |21prevents the short circuiting of the B-battery through the headphones,while the choke coil |26 prevents radio frequencies from entering thephones. The condenser or capacitor |32 permits the by-passing of radiofrequencies to the ground and is so designed as to not-materially affectaudio frequencies.

Another form of output connection is illustrated in Figure 3 of thedrawing. In this arran-gement the phones or sound reproducer |33 areconnected by a conductor |34 to one terminal of an antenna coil |35, theother terminal of which is grounded as illustrated at |36. Thecooperating coil of the antenna transformer, designated by the numeral31, has one terminal thereof connected by the conductor |39 to the inputterminal of the radio receiver A. This conductor |39 is connectedthrough the variable condenser |40 to the ground, the other terminal ofthe coil |35 is connected by the conductor |4| to the automatic volumecontrol terminal 69. This conductor |4| includes a connection throughthe condenser |42 to the ground. Thus the input circuit is identical tothat illustrated in Figures 1 and 2. The other phone lead |43 isconnected through a radio frequency choke coil |44 to the conductor|45.y A condenser |46 is provided between the conductor 45 and theconductor |41, which leads to the output terminal 92 of the radioreceiving set. A capacitor |49 is connected between the conductor |45and the ground. The conductor |50 leads through a resistor to thepositive B-battery terminal 9.

It will be noted in this circuit that the B- battery voltage is suppliedthrough the resistor to the output plate and this circuit is segregatedfrom the ear-phone circuit by means of the condenser |46. The radiofrequency choke coil 44 is so designed as to allow audio frequencies topass therethrough while choking or stopping radio frequencies. Thecapacitor |49 permits the by-passing of the radio frequencies to theground.

In Figure 4 of the drawing I disclose another modified form of circuit4which could be used. In this circuit the phones or sound reproducer |52and one phone cord or lead |53 which is connected to one end of aninductance coil |54, the other of which is connected to a conductor |55leading to the input terminal The con-I denser |56 is provided betweenthe conductor |55 and the conductor |51 secured to the input terminal. f

battery is connected through the resistor |10 to the output plate of theradio receiving set and this positive battery terminal is segregatedfrom the ground by means of the condenser |66. 'Ihe radio frequencychoke coil |64 is so constructed as to pass audio frequencies and tochoke or stop radio frequencies. nected between the conductor |65 andthe ground capable .of by-passing radio frequencies without materiallyaffecting the audio frequencies. Thus the radio frequencies areprevented from entering the phones or speaker 52.-

In order to illustrate a variety of specific connections which may bemade, Figure 5 illustrates another Inodied arrangement. In this circuitthe phones or speaker unit |12 have one phone cord or lead |13 which isconnected to one side of the condenser |14, the other side of which isconnected by conductor |15 to one end of the.

antenna coil |16. The other terminal of the coil |16 is connected byconductor |11 to one side of the condenser |19, the other terminal ofwhich is connected by conductor |80 to the input terminal of the radioreceiving set. The conductor |11 is connected to the variable condenser8| the opposite terminal of which is grounded. A tap |82 to anintermediate point on the coil |16 is also grounded. The conductor |80is connectedV by the conductor |83 to Vthe A. V. C. terminal 69.

In the event that the radio receiving set does not include automaticvolume control it is ob-V vious that the condenser |19 and the conductor|83 may be eliminated, the conductor |11 being directly connected to theinput terminal The other phone cord or lead |84 from the phones |12 isconnected to one end of the radio frequency choke coil |85, the otherterminal of which is connected by the conductor |86 to the outputterminal 92 of the radio receiving set. A conductor |81 connected to theconductor |86 1s electrically connected to one terminal of thelcondenser 89, the other terminal of which is leading to the firstdescribed phone terminal.

connected intermediate unev ends of the een |54, I provide a'lead |59which is grounded. The conductor |is also connected through a variablecondenser to the ground.

When automatic volume control is used in the radio receiving set theconductor |51 is connected by a conductor |6| through the resistor |62to the A. V. C. terminal 69. In case no automatic volume control isprovided the condenser |56, the conductor |'6|, and the resistor |62 areeliminated, the conductor |55 extending directly to the input terminal eThe other phone cord or lead |63 is connected to the radio frequencychoke coil |64, the opposite terminal of which is connected by conductor|Yto one side of the condenser |66. The other side of the condenser isconnected by conductor |61 to the output terminal l92 of the radioreceiving set A. The conductor |61 is also cone nected by a conductor|69 through a resistor |10 to the positive terminal of the B-battery.

It willb e noted VVthat in this circuit the B- Thus in this constructionthe phones are maintained at B-battery potential and the shortcirfcuiting ofthe B-battery is prevented by the condensers |14 and |89.

In this circuit it will be noted that the output plate is vconnected tothe phones through the radio frequency choke coil which will allow thepassage of audio frequency, but which will choke or stop radiofrequencies. Because of the fact that the phones are at B-batterypotential, it is also essential to have a second radio frequency chokecoil 9| between the positive terminal of the B-battery and the phones orsecond reproducer |12. The capacitor or condenser |89 allows theby-passing of radio frequencies to the ground.

In Figure '6 of the drawing still another modied form of circuit isillustrated. In this arrangement the phones |93 have one lead |94ltherefrom connected to one terminal of the antennacoil |95` forming apart of the input transformer |96; The'other terminal of the antenna Acapacitor |1| is con- One terminal of the other coil |99 of the inputtransformer |96 is connected by conductor 200 to the input terminal ofthe radio receiving set A. The conductor 200 is also connected to thevariable condenser 20|, the terminal Yof Which is grounded at 202.

The other terminal of the coil |99 is connected by conductor 203 to theA. V. C. terminal 69 of the radio receiving set. A condenser 204 isconnected to the conductor 203 and the other terminal of this condenseris grounded.

The other lead 205 from the phones |93 is connected to the radiofrequency choke coil 206, and the other terminal of this coil 206 isconnected by conductor 201 to one terminal of lthe condenser 299. Theopposite condenser terminal is connected by conductor 210 to the outputterminal 92 of the radio receiving set A. A capacitor 2|| is connectedto the conductor 291 and the other terminal of the capacitor isgrounded. The conductor 2|0 is connected through a suitable inductance2|2 to the B-battery terminal of the radio receiving set. In thisarrangement the output plate is supplied from the positive B batteryterminal through the vinductance coil 2|2, and this circuit issegregated from the second reproducer circuit lby the condenser 209. Theradio frequency choke coil 296 allows the passage of audio frequencyWaves, While choking or stopping the radio frequency Waves. These radiofrequencies may be by-passed to the ground by the capacitor 2| I.

In the foregoing description numerous illustrative circuits have beendescribed for the purpose of illustrating that a considerable number ofspecific hook-ups could be used, While still employing the secondreproducerand the leads thereto as an antenna. It should be noted thatall of the cir-cuits have certain features in common. In the first placethe ear-phones are connected in such a Way that the radio frequencyWaves are prevented from passing into the earphones or other soundreproducer. In the second place a capacitor is provided for icy-passingradio frequency Waves. In the third place the B-battery circuit to theplate of the output tube is so arranged that the short circuiting of theB-battery through the second reproducer circuit is prevented.

For the purpose of simplicity I have used the term sound reproducer inthe claims in place of calling for ear-phones or a speaker unit. Whileear-phones are ordinarily used with the portable sets for which thisarrangement is particularly adapted, speakers are sometimes used, andsuch speaker could be used in place of the ear-phones described. Forthis reason the term sound reproducer is meant to designate any soundreproducer element, such as ear-'phones or a speaker unit.

In accordance with the patent statutes, I have described the principlesof construction and operation of my antenna systems, and While I haveendeavored to set forth the best embodiment thereof, I desire to have itunderstood that these are only illustrative of a. means of carrying outmy invention, and that obvious changes may be made Within the scope ofthe following claims Without departing from the spirit of my invention.

I claim:

1. A radio receiving system comprising in com- :'bination, a receiverhaving a radio frequency input circuit including an antenna coil havingcoupled primary and secondary portions, detecting and amplifying tubes,and an audio frequency out-put circuit including an out-put transformer,ear phones, a radio frequency choke coil connected in series between oneterminal of the ear phones and one terminal of the out-put transformersecondary, the other terminal of said secondary being grounded, aby-pass circuit connected to said one terminal of said out-puttransformer secondary, including a capacitor of a size to by-pass radiofrequencies and not to by-pass audio frequencies, and said choke coilbeing of proper size to separate the radio and audio frequencies and toprevent the radio frequencies from being grounded or bypassed to groundthrough the secondary of the out-put transformer or the capacitor, andmeans connecting the other terminal of said phones to one terminal ofthe antenna coil primary portion, the other terminal of the said primaryportion being grounded, whereby radio frequency potentials impressedupon the named circuit elements and connections are applied to saidreceiver input circuit through said secondary portion.

2. In a radio receiving system having a radio frequency input side andan audio frequency out-put side, an antenna transformer having a primaryWinding arranged to transmit radio frequency signalling impulses to theinput side, an out-put transformer connected to the audio frequencyout-put side, ear phones having one terminal thereof connected in seriesthrough a radio frequency choke coil to one terminal of the out-puttransformer secondary, the other terminal of ths vtransformer secondarybeing grounded; a by-pass connected to said one terminal of saidtransformer secondary and ground and including a capacitor capable ofby-passing radio frequencies and not by-passing audio frequencies, saidchoke coil constructed to stop radio frequencies from being grounded orbypassed to ground through the secondary of the out-put'J transformer orthe capacitor; and means connecting the other terminal of said earphones to one terminal of the primary Winding of said antennatransformer, the other terminal of said primary winding beingl grounded,thus completing both radio frequency and audio frequency circuits.

3. In a radio receiving system having a radio frequency input side andan audio frequency7- out-put side, an antenna transformer having aprimary Winding arranged to transmit radio frequency signalling impulsesto the input side, an out-put transformer connected to the audiofrequency output side, sound reproducing means having one terminalthereof connected in series through a radio frequency choke coil to oneterminal of the out-put transformer secondary, the other terminal ofthis transformer being grounded; a 'by-pass connected to said oneterminal of said transformer secondary and ground and including acapacitor capable of by-passing radio frequencies and not by-passingaudio frequencies, sai-d choke coil constructed to stop radiofrequencies from being grounded or by-passed to ground through thesecondary of the out-put transformer or the capacitor; and meansconnecting the other terminal of said sound reproducing means to oneterminal of the primary winding of said antenna transformer, the otherterminal of said primary Winding being grounded, thus completing bothradio frequency and audio frequency circuits, Y

BARTON T. SETCHELL.

